Inheriting (subclass) of dict data attribute (copying)

[Aaron S. Hawley]

On Sun, 27 Jul 2003, Aaron S. Hawley wrote:

> [What] Would be the most obvious (best in idiom) to overwrite the
> dictionary of my derived dict class?  The old school way is obvious to
> me.
>
> TIA, /a
>
> #!/usr/bin/env python
>
> from UserDict import UserDict
>
> class Old_Chickens(UserDict): ## old school
>     def __init__(self, chickens):
>         self.set_chickens(chickens)
>     def set_chickens(self, chickens):
>         self.data = chickens
>
> class New_Chickens(dict): ## new school
>     def __init__(self, chickens):
>         self.set_chickens(chickens)
>     def set_chickens(self, chickens):
>         self = dict.__init__(self, chickens)
>
>
> new_chickens = New_Chickens({'white': 12, 'brown': 8})
> print new_chickens['white']
>
> old_chickens = Old_Chickens({'white': 12, 'brown': 8})
> print old_chickens['white']

this would probably be fine:

#!/usr/bin/env python

from UserDict import UserDict

class Old_Chickens(UserDict): ## old school
    def __init__(self, chickens):
        UserDict.__init__(self) #FIX: be sure to call the base __init__
        self.set_chickens(chickens)
    def set_chickens(self, chickens):
        self.data = chickens

class New_Chickens(dict): ## new school
    def __init__(self, chickens):
        dict.__init__(self) #FIX: again, be sure to call the base __init__
        self.set_chickens(chickens)
    def set_chickens(self, chickens):
        dict.__init__(self, chickens) #FIX: you need only recall __init__

...

try reading the "Unifying types and class in Python 2.2" before posting
a question about subclassing types:

http://www.python.org/2.2/descrintro.html